1. Field of the Invention
The present invention relates to a semiconductor acceleration detecting apparatus and, in particular, to a semiconductor acceleration detecting apparatus in which resistance to impact is improved.
2. Description of the Related Art
FIG. 3 is a sectional side view showing a conventional semiconductor acceleration detecting apparatus. FIG. 4 is a perspective view thereof. In FIGS. 3 and 4, an acceleration detection beam 1 is mounted on a board 2 by a supporting base 3 mounted on the end of the acceleration detection beam 1. A weight 4 for increasing the sensitivity to acceleration is disposed on the other end of the acceleration detection beam 1. A U-shaped fastener 10 for controlling the upward and downward movement of the weight 4, i.e., the movement in response to acceleration, is mounted on the board 2 below and above this weight 4. A groove 5 faces the board 2 approximately in the middle of the acceleration detection beam 1. Formed on the rear surface of this groove 5 is a strain resistor 6 whose resistance value changes according to the tension and compression thereof. Electrical signals from this strain resistor 6 are transferred to an extraction pin 7 by a conductor 8. The board 2, the acceleration detection beam 1, and the fastener 10 are covered with the lid 9 of an enclosure. FIG. 4 shows a state before the lid 9 is mounted onto the board 2.
With the conventional semiconductor acceleration detecting apparatus constructed as described above, when acceleration is applied to a semiconductor acceleration detecting apparatus, the acceleration detection beam 1, in particular, at the groove 5, flexes. At this time, as the result of the strain resistor 6 disposed on the acceleration detection beam 1 opposite the groove 5, the resistance value of the strain resistor 6 changes. Its output signals are extracted from an extraction pin 7 via the conductor 8, and acceleration is detected. Breakage of the acceleration detection beam 1 due to a large impact is prevented by controlling the upward and downward flexing of the acceleration detection beam 1.
In such a semiconductor acceleration detecting apparatus as described above, when an acceleration other than in a vertical direction is applied, the weight 4 response in that direction. However, the fastener 10 cannot control variations in the position of the weight 4 other than in the vertical direction. Therefore, there is a problem in that the flexing and twisting displacement of the acceleration detection beam 1 cannot be controlled with a high degree of accuracy.